1. Field of Invention
This invention relates to high-pressure fluid conduit connections and more particularly to such connections useful in a fuel injection system for internal combustion engines.
2. Description of the Prior Art
Fuel injection systems for internal combustion engines are known which have a connection stub, a high-pressure line, a lock nut, and a sealing face, wherein the connection stub has a bore and a thread that are disposed concentrically to its longitudinal axis, and the high-pressure line on its end has a counterpart corresponding to the sealing face, which counterpart is pressed onto the sealing face by the lock nut screwed to the connection of this type stub. A high-pressure connection is known from German Published, Nonexamined Patent Application DE-OS 198 08 882 A1, in which a frustoconical sealing face adjoins the center bore of the connection stub. The corresponding counterpart of the high-pressure line is pressed onto this sealing face by means of a lock nut. This produces a sealing connection between the connection stub and high-pressure line.
A disadvantage of this known high-pressure connection is that the high-pressure line must extend precisely in the direction of the longitudinal axis of the connection stub, since the high-pressure connection allows no angular compensation.
The object of the present invention is to furnish a high-pressure connection which compensates for errors of alignment between the longitudinal axis of the connection stub and the high-pressure line, without sacrificing the tightness of the high-pressure connection and without requiring the high-pressure line to absorb undesired bending stresses.
This object is attained according to the invention by a high-pressure connection for a fuel injection system for internal combustion engines, which comprises a connection stub, a high-pressure line, a lock nut, and a sealing face, wherein the connection stub has a bore and a thread that are disposed concentrically to its longitudinal axis, and the high-pressure line on its end has a counterpart corresponding to the sealing face, which counterpart is pressed onto the sealing face by the lock nut screwed to the connection stub, and wherein the sealing face and the faces oriented toward one another of the lock nut and the counterpart have the form of a dome, and that the center points of the domes occupy the same geometric location.
Because of the spherical design of the sealing face, the counterpart and the lock nut, the high-pressure line can be introduced into the connection stub with errors of alignment, without this having any effect on the sealing face of the connection stub and of the counterpart. Thus in these cases as well, the tightness of the high-pressure connection is preserved in full. Furthermore, no unnecessary bending stresses, which lead to increased material stress, are introduced into the high-pressure line.
In one feature of the invention, the dome, toward the lock nut, of the counterpart is embodied as spherical ring disk, so that when the lock nut is tightened, the high-pressure line is not turned, and moreover the spherical ring disk can be made from a different material from the high-pressure line and its counterpart.
In another embodiment of the invention, a clamping ring is disposed between the lock nut and the counterpart, and its face toward the counterpart takes the form of a dome, so that because of the greater structural length, the seating of the counterpart in the sealing face causes only a slight lessening in the contact pressure.
In a further variant, the faces oriented toward one another of the clamping ring and lock nut are circular-annular faces, so that the friction between the clamping ring and the lock nut becomes minimal.
Another variant of the invention provides that the through bores of the lock nut and clamping ring are embodied conically, and the bore diameter increases as the spacing from the sealing face increases, so that even if there are relatively major errors of alignment, the high-pressure line can be introduced without deformation into the connection stub and screwed to it.
In a further aspect of the invention, the cone angle of the through bores is less than or equal to 10xc2x0, so that a maximum allowable error of alignment can be defined by the choice of the cone angle.
According to the invention, the connection stub is welded to a high-pressure fuel reservoir, to the housing of a high-pressure fuel pump, or to the housing of an injection valve, so that the connection stub can be manufactured separately and can be joined in a simple, economical way to the high-pressure fuel reservoir or to one of the aforementioned housings.
Another variant provides that the connection stub is screwed to a high-pressure fuel reservoir, to the housing of a high-pressure fuel pump, or to the housing of an injection valve, so that the high-pressure connection according to the invention can be used even in existing injection systems by being exchanged for the existing high-pressure connections.
In a further feature of the invention, the connection stub and the high-pressure fuel reservoir, the connection stub and the housing of the high-pressure fuel pump, or the connection stub and the housing of the injection valve are embodied in one piece, in particular as a forged part, so that the number of components and joining connections is minimized. Furthermore, a favorable course of material stress can be achieved.
Another embodiment of the invention provides that the sealing face is part of the high-pressure fuel reservoir, of the housing of the high-pressure fuel pump, or of the housing of the injection valve, so that the structural height of the high-pressure connection of the invention is reduced.
In another variant, the sealing face is part of the connection stub, so that the high-pressure connection can be produced independently of the other component groups of the fuel injection system and economically. Furthermore, the geometrical association of the connection stub and the sealing face is always preserved.
A feature of the invention provides that the lock nut has a female thread, and the connection stub has a corresponding male thread, so that the rated diameter of the thread is markedly greater than the outside diameter of the sealing face, and thus high contact pressures are feasible.
In a further feature of the invention, the lock nut has a male thread, and the connection stub has a corresponding female thread, so that the outer diameter of the connection stub and thus the requisite installation space as well are minimized.
The objects stated above are also attained by a fuel injection system for internal combustion engines, having a high-pressure connection, which has a connection stub, a high-pressure line, a lock nut, and a sealing face, wherein the connection stub has a bore and a thread that are disposed concentrically to its longitudinal axis, and the high-pressure line on its end has a counterpart corresponding to the sealing face, which counterpart is pressed onto the sealing face by the lock nut screwed to the connection stub, and wherein the sealing face and the faces oriented toward one another of the lock nut and the counterpart have the form of a dome, and that the center points of the domes occupy the same geometric location.